Board Thread:Off Topic/@comment-30458103-20161124024530/@comment-30588928-20161124163715

This could be a future side quest assigned by Gym Leader Chad.

In the core series games Pokemon Ruby, Sapphire, and Emerald, Gym Leader Wattson assigns the player to go to the underground sector of Mauville City called New Mauville. He tells the player that the generator there has been running haywire and is unsafe. He then gives the player a key to access New Mauville. Once the quest is complete, he rewards the player with TM24 Thunderbolt.

This cellar will probably be the location of a similar quest.